Hi,
I'm trying to validate an Archimedean spiral antenna with inner radius of 3mm, outer radius of 10mm, 8 turns with 16 segments/turn to operate between 0 to 4GHz in free space, using CST MWS (please refer to attachment 'a').
I used a discrete port (with an impedance set at 188.5 ohm due to self-complementary structure) with an open (add space) boundary condition for all dimensions.
What concerns me is that the VSWR gives a ringing effect at these region. Is it acceptable to have this kind of result?, because in the paper that I refer to have a straight line instead (please refer to attachment '1' and '2').
Please help me.. Thank you!